The present invention relates to devices for providing an electrical indication of the relative position of a movable member. In particular the invention relates to devices where it is desired to provide the relative position of a selector member movable by a vehicle operator for selecting the desired mode of operation of the vehicle drive transmission. In certain automotive applications, it is desired to provide an electrical signal to an on-board electronic microcomputer, employed for transmission operational control, of the position of the selector member as an indication of the vehicle operator's selection for the drive mode.
Transmission selector position indicators for automotive applications must provide relatively long life and reliable and repeatable operation in an environment of transmission hydraulic fluid, engine oil, and road dirt. In such applications, it is desired to provide the selector position indicator interiorly of the transmission housing or casing and provide an externally accessible electrical connector for the electrical leads to the on-board computer circuitry. Where such a transmission selector position indicator has been mounted through the wall of the transmission casing, problems have been encountered in positioning the actuator portions of the indicator accurately with respect to the movable selector mechanism. Problems have also been encountered in providing accuracy of position indication due to the dimensional tolerances of the location of the position indicator and the dimensional variations of the selector members.
Heretofore, where it has been desired to provide an electrical indication of the relative position of an automotive transmission selector, plural electrical assemblies have been employed, disposed at selected spaced circumferential locations about the pivoted member of the selector mechanism within the transmission casing. Typically, plural plunger-actuated electrical switches would be disposed through the transmission casing with the plungers contacting detent surfaces on the pivoted selector member. Although this arrangement has been used in mass-produced automotive transmissions for passenger cars, problems have been encountered for accurately locating the switch actuation plungers within the transmission casing, with respect to the detent surfaces on the pivoted selector member. The problems of dimensional variation and accuracy of location of the plural switches have made it desirable to find another way or means of providing an accurate electrical indication of the transmission mode selector position.